Internal combustion engines rely on a steady or regular supply of lubricant to ensure that moving parts of the engine does not overheat or get subjected to excessive wear. Power tools are often equipped with engines that are provided with lubricant along with the fuel. This is often achieved by mixing the lubricant into the fuel in advance. The supply of lubricant can however also be performed automatically by a pump providing lubricant to the engine from a separate lubricant supply. Since mixing lubricant and fuel manually to the right proportions can be difficult and purchasing premixed fuel/lubricant mixture is more expensive than buying the lubricant and fuel separately, an engine with an automatic lubrication system is often preferred.
However, when the lubrication is performed automatically by the engine, it is important that the lubrication system is reliable since the user is unable of controlling that the right amount of lubricant is provided to the engine.
It is known in the art (related background art can be found for instance in US20130291831A1) to provide a sensor for detecting if lubricant is present in a lubrication conduit; however merely detecting if lubricant is present has proven unreliable since standing oil may be interpreted as a flow of lubricant. Since flow sensors are considered too complex and are expensive, a reliable and cost effective way of ensuring that lubricant is flowing in a conduit is preferred.